1. Field of the invention
The present invention relates to a lamp-lighting device, specifically, to that which supplies a direct current obtained by rectifying an alternating current with full-wave rectifier and smoothing means to a lamp.
2. Description of the prior art
Recently, various flickerless illuminating devices that are easy on the eye when used for hours have been developed, and some of them have been commercialized.
The present inventor discloses in Japanese Patent Laid-Open No. 193,398/86, Japanese Patent Laid-Open No. 185,516/87 and Japanese Utility Model Laid-Open No.278,782/86 that, when lighted with a direct current obtained by rectifying an alternating current with combination of full-wave rectifier and smoothing means, a lamp provides a flickerless illumination that is easier on the eye even when used for hours than that attained by energization of an alternating current.
Although such conventional lamp-lighting device attains a satisfactory illumination, it has the drawback that, when conventional ac 100 volts is used, it may extremely shorten lamp life because a direct current obtained by rectifying conventional ac 100 volts with such combination elevates the voltage across filament up to 140 volts at maximum that is 140% higher than its rating.